Two points,A and B,are on a disk that rotates about an axis.Point A is closer to the axis than point B.Which of the following is not true?
A)Point B has the greater speed.
B)Point A has the lesser centripetal acceleration.
C)Points A and B have the same angular acceleration.
D)Point B has the greater angular speed.
E)Point A has the lesser tangential acceleration.

Question

Quizplus · Accepted Answer

Since point A is closer to the axis than point B, it will have a smaller distance to cover in one revolution compared to point B. Therefore, point A will have a smaller angular speed than point B. Hence, option D is not true. Option A is true because point B, being farther from the axis, will cover a greater distance in one revolution and, thus, will have a greater speed. Option B is also true because the centripetal force acting on a point is inversely proportional to its distance from the axis. Since point A is closer to the axis, it will experience a lower centripetal force and, hence, a smaller centripetal acceleration. Option C is true because all points on the rotating disk have the same angular acceleration since they all move with the same angular displacement in the same time interval. Finally, option E is also true because the tangential acceleration of a point on a rotating disk is directly proportional to its radial distance and angular acceleration. Since point A is closer to the axis and has a lower radial distance, it will have a smaller tangential acceleration.

Two Points,A and B,are on a Disk That Rotates About